Conventional latches are used to restrain the movement of one member or element with respect to another. For example, conventional door latches restrain the movement of a door with respect to a surrounding door frame. The function of such latches is to hold the door secure within the door frame until the latch is released and the door is free to open. Existing latches typically have mechanical connections linking the latch to actuation elements such as handles which can be actuated by a user to release the latch. Movement of the actuation elements is transferred through the mechanical connections and (if not locked) can cause the latch to release. The mechanical connections can be one or more rods, cables, or other suitable elements or devices. Although the following discussion is with reference to door latches (e.g., especially for vehicle doors) for purposes of example and discussion only, the background information and the disclosure of the present invention provided applies equally to a wide variety of latches used in other applications.
Most current vehicle door latches contain a restraint mechanism for preventing the release of the latch without proper authorization. When in a locked state, the restraint mechanism blocks or impedes the mechanical connection between a user-operable handle (or other door opening device) and a latch release mechanism, thereby locking the door. Many conventional door latches also have two or more lock states, such as unlocked, locked, child locked, and dead locked states. Inputs to the latch for controlling the lock states of the latch can be mechanical, electrical, or parallel mechanical and electrical inputs. For example, by the turn of a user's key, a cylinder lock can mechanically move the restraint mechanism, thereby unlocking the latch. As another example, cable or rod elements connecting a door lock to the restraint mechanism can be controlled by one or more electrical power actuators. These actuators, sometimes called “power locks” can use electrical motors or solenoids as the force generator to change between locked and unlocked states.
An important issue with regard to the design of latch assemblies is the desirability of a latch assembly to operate smoothly. Unless friction is employed to retain one or more elements in desired positions in the latch assembly, low-friction contact (such as contact between rotatably-connected elements) is preferred. In addition, latch assembly designs in which part wear is reduced or eliminated is highly desirable. These latch assembly design considerations significantly limit the number of viable solutions for a number of latch assembly design problems described below.
In most conventional latch designs, one or more elements are moved to release a retaining element holding the latch in a latched position. For example, a pawl can be movable to release a ratchet holding the striker of the latch. The pawl (or other movable element used to hold the ratchet in a latched position) can be moved in many different manners, such as by being rotated, pushed, pulled, shifted, and the like. Typically, one or more elements such as levers are movable by actuation of a handle or other latch assembly input to move the pawl. These pawl-moving elements can be connected directly to the pawl or can otherwise be moved to exert motive force upon the pawl. In either case, preventing inadvertent movement of the pawl by these pawl-moving elements is another important design consideration, and can be accomplished by controlling the position and mobility of the pawl-moving elements in the latch assembly. Such inadvertent movement can be caused in some conventional latch assemblies by employing pawl-moving elements that have a mass close to the pawl and that can react to shock or severe vibration to impart force upon the pawl, by severe impact upon the latch (such as experienced in a vehicle collision or rollover), and by other manners.
Because many pawl-moving elements have locked and unlocked states as described above, such elements must often be moved or movable in different manners corresponding to the locked and unlocked states. Such movement can limit the ability to fully secure and control the pawl-moving element within the latch assembly (both highly desirable features of pawl-moving elements). Therefore, the possible manners in which pawl-moving elements can be connected and move within latch assemblies is often significantly limited.
It is possible to add structure and elements to conventional door latch designs in order to address the above-noted problems and to take into account the latch assembly design considerations described above. However, such additional structure and elements are likely to increase latch complexity. Increased latch complexity also increases assembly and repair cost. Accordingly, the reasonable door latch design alternatives available to address the above-noted problems and design considerations of conventional door latches are significantly limited.
Problems of latch weight and size are related to the problem of latch complexity. The inclusion of more elements and more complex mechanisms within the latch generally undesirably increases the size and weight of the latch. In virtually all vehicle applications, weight and size of any component is a concern. Therefore, many latch designs employing additional structure and elements to address the above-noted problems and to take into account the design considerations described above do so at an unacceptable cost of increased latch weight and size.
Regardless of the mechanism employed to change the locked state of a latch assembly (to disable or enable a mechanical or electrical input to the latch assembly), another problem common to the vast majority of conventional door latches relates to the inability of such door latches to properly respond to multiple inputs at a given time. A well-recognized example of this problem is the inability of most conventional door latches to properly respond to a user unlocking the door latch while the door handle is partially or fully actuated. While this problem can exist for door latches that are not powered, it is particularly problematic in powered latches. For example, a user of a keyless entry system can push a button on a key fob, enter an access code on a door keypad, or otherwise transmit a signal (by wire or wirelessly) to a controller in the vehicle that in turn sends a signal to power unlock a handle input to the latch. In conventional power latches, an amount of time is required for this process to take place. During this time, a user may attempt to unlatch the latch by actuating the handle input. Because the latch has not yet been unlocked, such actuation does nothing—even after the latch has been powered to its unlocked state while the handle input is in a partially or fully actuated position. The user must release the handle, transmit another unlocking signal to power unlock the handle, and then re-actuate the handle to unlatch the latch. In other words, to unlatch a conventional latch, actuation of the handle input must occur after the handle input has been placed in its unlocked state. Partial or full actuation of the handle input before this time will not unlatch the latch and will require the user to release and re-actuate the handle input.
This shortcoming of conventional door latches exists for powered and fully manual door latches alike. In addition to requiring the user to re-actuate an input to unlatch the unlocked latch, this problem can even prevent the latch from changing between its locked and unlocked states. In such a case, the user is required to unlock the latch assembly again (re-transmit a signal to the latch assembly or manually unlock the latch assembly again as described above) after the handle input has been released. Any of the results just described represent an annoying attribute of conventional latch assembly designs. In this and other examples, a conventional latch assembly is unable to respond to actuation of more than one input at a time, or is only responsive to one of two inputs actuated simultaneously or closely in time.
In light of the problems and limitations of the prior art described above, a need exists for a latch assembly that is relatively simple in construction, lightweight, reliable, and easy to assemble and maintain, operates smoothly and efficiently with minimal friction and wear, has pawl-moving elements having improved control and stability, is preferably able to properly respond to an unlocking/locking input and to an latching/unlatching input received simultaneously or closely in time, and does so with minimal to no additional latch assembly elements and structure. Each preferred embodiment of the present invention achieves one or more of these results.